遠方クエーサー分子吸収線系における リチウム同位体比の測定 ALMA cycle 6 プロジェクト “Lithium isotope ratio in ISM at z=0.68” の概要

Yuki Yoshimura (The Univ. of Tokyo)

Collaborators: K. Kohno, Y. Nishimura, B. Hatsukade (The Univ. of Tokyo) W. Aoki, T. Matsuno, T. Izumi (NAOJ), Y. Tamura, M. Lee (Nagoya Univ.)

Cosmic Shadow 2018 ~クェーサー吸収線系でみる宇宙~ @石垣島 2018.11.24 - 25

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Outline

‣ Lithium isotope ratio measurement at high-z ✓Cosmological lithium problem ✓Difficulties in existing probes ✓ALMA cycle 6 project

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‣ High-z millimeter wave molecular absorption line systems (short talk) ✓Unique laboratories at high-z ✓Only a handful of absorbers are known to date. ✓ Survey to detect new absorbers

➡ many attempts but many failures ✓What is the next survey strategy?

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Outline

‣ Lithium isotope ratio measurement at high-z ✓Cosmological lithium problem ✓Difficulties in existing probes ✓ALMA cycle 6 project

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‣ High-z millimeter wave molecular absorption line systems (short talk) ✓Unique laboratories at high-z ✓Only a handful of absorbers are known to date. ✓ Survey to detect new absorbers

➡ many attempts but many failures ✓What is the next survey strategy?

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Introduction: Cosmological lithium problem

‣ SBBN+CMB prediction of primordial abundances of the light elements ✓Deuterium and 4He

➡ Good agreement with observations (e.g., Cooke+14, Izotov+14)

✓7Li (and 6Li?) ➡ Significant mismatch with observations

(e.g., Asplund+06) ➡ The lithium problem

‣ Possible solutions to the lithium problem ✓Astrophysical systematics in observations ✓Miscalculation in nuclear reactions ✓Physics beyond the standard model

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Green: observational abundances Blue: Standard model predictions

Pitrou et al. 2018

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Deuterium abundance measurements

‣ Very metal-poor high-z DLA ✓Deuterium production sources are unspecified ➡ Observed value will be primordial

✓Strong dependence on the baryon density ➡ Not so affected by effective neutrino number

�5DI DICooke et al. 2014Pitrou et al. 2018

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4He abundance measurement

‣ Low metallicity HII region in nearby galaxies ✓Assume linear relationship between Yp and O/H ✓Extrapolate the relationship to O/H = 0

�6Izotov et al. 2014

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7Li abundance measurements

‣ Spite plateau (Spite & Spite 1982) ✓Lithium abundances have been measured in unevolved halo-stars. ✓7Li abundances are almost constant in wide metallicity range.

➡ Independent of the Galactic chemical evolution -> primordial

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CMB+BBN

Spite plateau

Fields et al. 2011

Disagreement

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6Li abundance measurements

‣ Asplund upper envelope (Asplund et al. 2006) ✓6Li production in BBN is negligibly small. ✓Main source of 6Li is Galactic Cosmic-Rays (GCR) spallation of CNO nuclei. ✓Observational abundances of 6Li are inconsistent to GCR prediction.

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CMB+BBN

Asplund upper envelope

GCR prediction

Fields et al. 2011

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Difficulties of the observation toward stellar atmospheres

‣ Difficulties of the modeling of stellar atmospheres ✓Li depletion processes are possible (but unspecified). ✓6Li can be detected with 1D LTE (Asplund et al. 2006),

but NOT with 3D non-LTE (Lind et al. 2013).

‣ Line broadening ✓Wavelength of the isotoplogue atomic absorption lines are very close.

�9Asplund et al. 2006

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Lithium abundance in ISM

‣ Li absorption has been detected along the sight lines of bright stars ✓In MW ISM (e.g., Kawanomoto+09) and in SMC ISM (Howk+12)

‣ Li isotope ratio 6Li/7Li in ISM ✓Line broadening is less significant than in stellar atmosphere ✓The effects of ionization and dust-depletion are canceled

�10Kawanomoto et al. 2009 Howk et al. 2012

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Lithium abundance in ISM

‣ Li absorption has been detected along the sight lines of bright stars ✓In MW ISM (e.g., Kawanomoto+09) and in SMC ISM (Howk+12)

‣ Li isotope ratio 6Li/7Li in ISM ✓Line broadening is less significant than in stellar atmosphere ✓The effects of ionization and dust-depletion are canceled

�10Kawanomoto et al. 2009 Howk et al. 2012

Existing observations are limited in the local universe and have some difficulties.

We need new (independent) and distant probes of Li abundance!

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LiH as a new and independent probe of Li

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‣ Tentative (~3σ) detections of LiH toward B0218+357(?) ✓B0218+357: BL Lac object at z~0.94 ✓Absorber: spiral galaxy at z = 0.68466 ✓Target line: 7LiH (1-0) at 444GHz (rest-frame)

LiH as a new and independent probe of Li

�11Combes & Wiklind 1998, using IRAM 30m

Friedel et al. 2011, using CARMA

(c)IRAM

(c)M. C. H. Wright

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‣ Tentative (~3σ) detections of LiH toward B0218+357(?) ✓B0218+357: BL Lac object at z~0.94 ✓Absorber: spiral galaxy at z = 0.68466 ✓Target line: 7LiH (1-0) at 444GHz (rest-frame)

LiH as a new and independent probe of Li

�11Combes & Wiklind 1998, using IRAM 30m

Friedel et al. 2011, using CARMA

(c)IRAM

(c)M. C. H. Wright

Primarily due to the lack of sensitivity, previous detections are uncertain.

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‣ Approved and now waiting for the data delivery

ALMA cycle 6 project

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Target: B0218+357

‣ A high-z molecular absorption line system at z=0.68 ✓Lensed BL Lac object at z~0.94 ✓Lensing galaxy is a spiral galaxy at z=0.68 and its ISM is absorber.

➡ LiH absorption lines are redshifted into the atmospheric window. ✓Molecular absorption was first discovered by Wikinlind & Combes 95. ✓Many molecules have been discovered (e.g., Wallstrom+16).

�13(c)NASA’s Goddard Space Flight Center

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Target: B0218+357

‣ A high-z molecular absorption line system at z=0.68 ✓Lensed BL Lac object at z~0.94 ✓Lensing galaxy is a spiral galaxy at z=0.68 and its ISM is absorber.

➡ LiH absorption lines are redshifted into the atmospheric window. ✓Molecular absorption was first discovered by Wikinlind & Combes 95. ✓Many molecules have been discovered (e.g., Wallstrom+16).

�13(c)NASA’s Goddard Space Flight Center

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Target: B0218+357

‣ A high-z molecular absorption line system at z=0.68 ✓Lensed BL Lac object at z~0.94 ✓Lensing galaxy is a spiral galaxy at z=0.68 and its ISM is absorber.

➡ LiH absorption lines are redshifted into the atmospheric window. ✓Molecular absorption was first discovered by Wikinlind & Combes 95. ✓Many molecules have been discovered (e.g., Wallstrom+16).

�132h21m05.44s05.46s05.48s05.50s05.52s

RA (J2000)

+35�56013.400

13.600

13.800

14.000

14.200

Dec

(J20

00)

0.3”

ALMA Band 7 image

(c)NASA’s Goddard Space Flight Center

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Comparison with a fiducial model

‣ A “realistic” model provided by Prantzos et al. 2012 ✓Assuming SBBN, standard GCR and realistic stellar production ✓The dependence of galactcentric distance is also predicted.

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0 2 4 6 8 10 12Time [Gyr]

0.00

0.05

0.10

0.15

0.20

0.25

0.30

6 Li/7 L

i

z=0.68

Proposed 5� sensitivity

Prantzos+12SolarAsplund+06 (Star)Kawanomoto+09(ISM)Howk+12 (SMC)Friedel+11 (LiH)

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Can we convert 6Li/7Li to 7Li/H?

‣ We need models for galaxies other than MW. ‣ Further observation toward B0218+357 in other wavelength to determine the detailed profiles (e.g., SFR, [Fe/H],…) of the absorber.

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Kajino et al. 2000

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Atomic lines can be detected?

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Li atomic lines at z = 0.68466

(c)WINRED

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Summary

‣ Lithium isotope ratio in ISM at z = 0.68 ✓There are pressing need for new probes of the (primordial) lithium abundance. ✓We are conducting the measurement of 6Li/7Li in ISM at z = 0.68 molecular absorber B0218+357 using ALMA. ➡ Status: All data taken -> waiting for the data delivery

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Summary

‣ Lithium isotope ratio in ISM at z = 0.68 ✓There are pressing need for new probes of the (primordial) lithium abundance. ✓We are conducting the measurement of 6Li/7Li in ISM at z = 0.68 molecular absorber B0218+357 using ALMA. ➡ Status: All data taken -> waiting for the data delivery

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Stay tuned!